1. Field of the Invention
The present invention relates to a liquid droplet discharge head, a manufacturing method thereof, and an image forming apparatus, and more specifically to the structure of a droplet discharge head that provides a discharge force to a liquid by deforming a piezoelectric member to discharge droplets from a nozzle, to a manufacturing method thereof, and also to an inkjet recording apparatus or another image forming apparatus that forms an image on a recording medium using this liquid discharge head.
2. Description of the Related Art
An inkjet-type recording apparatus deposits ink droplets on a printing medium by moving recording paper or another such printing medium relative to a recording head with nozzles and discharging ink from the nozzles according to a print signal, and forms an image on the printing medium by means of the inkjet.
Japanese Patent Application Publication Nos. 6-23987, 8-20109, 8-336967, 9-277528, and 9-300614 disclose an inkjet recording head that utilizes a cylindrical piezoelectric actuator. The recording head depicted in Japanese Patent Application Publication No. 6-23987 has a structure wherein a plurality of cylindrical tubes having ink spray ports (orifices) are aligned in a row on a pedestal, and the ink in the tubes is pressured and discharged as ink droplets from the orifices by deforming the cylindrical tubes through the electrostriction of an electrostrictive transducer disposed facing the pedestal surface on either side of the row of cylindrical tubes. This same reference publication introduces a system for mounting cylindrical electrostrictive elements on the side of the cylindrical tubes (transducer cylinder system).
Japanese Patent Application Publication No. 8-20109 proposes a method for manufacturing a cylindrical layered piezoelectric member by immersing a holed pattern member containing a part for forming a pillar-shaped pressure chamber alternately in an electrode material solution and a piezoelectric material solution a plurality of times, then performing a baking step.
Japanese Patent Application Publication No. 8-336967 proposes forming a piezoelectric member on the surface of a metal cylinder by a hydrothermal synthesis method.
Japanese Patent Application Publication No. 9-227528 proposes a manufacturing method wherein a plurality of holes are formed at equal intervals in a straight line on a hollow frame that serves as an ink supply unit, a pin composed of a resin wire or the like (a material that vaporizes and disappears in high-temperature environments) is fixed in place in each hole, a piezoelectric material is applied by means of a slurry immersion step onto part of a frame supporting the peripheries and base ends of these pins, the pins are melted by a baking step after drying, and a common electrode is formed on the inner surface of the piezoelectric member while an individual electrode is formed on the outer surface in a plating step.
Japanese Patent Application Publication No. 9-300614 proposes a manufacturing method wherein a plurality of holes are formed at equal intervals in a straight line on a hollow frame that serves as an ink supply unit, a tube-shaped electrode is fixed in place in each hole, a piezoelectric material is applied by means of a slurry immersion step onto part of a frame supporting these tube-shaped electrodes and their base ends, a baking step after drying is conducted, and then an individual electrode is formed on the outer peripheral surface of the piezoelectric member in a plating step.
The so-called cylindrically compressing piezoelectric heads disclosed in Japanese Patent Application Publication Nos. 6-23987, 8-20109, 8-336967, 9-277528, and 9-300614 have merits in that the ink in the cylindrical liquid chamber (in the pressure chamber) is pressurized in the direction facing diametrically inward from the side external periphery; therefore, the ink has a strong flying force.
Currently, however, further improvements in discharge force and higher refilling speeds are needed from the standpoint of diversifying ink liquids, controlling the occurrence of discharge problems, increasing the speed of printing, and the like.
The present invention has been contrived in view of such circumstances, and an object thereof is to provide a droplet discharge head and an image forming apparatus that uses this droplet discharge head, whereby it is possible to improve discharge efficiency and to increase the speed of refilling.
When a system of wrapping a green sheet around a cylindrical tube (glass tube) is used as the method for manufacturing the head as is shown in Japanese Patent Application Publication No. 6-23987, the tube diameter must be increased to allow for ease of handling of the entire tube in the manufacturing step, and therefore the nozzle cannot be provided with a high density.
Otherwise, as shown in Japanese Patent Application Publication Nos. 8-20109, 9-277528, and 9-300614, the method of performing baking after forming a piezoelectric member by immersion is impractical because immersion must be repeated a plurality of times in order to obtain the desired piezoelectric member thickness and plate thickness, which requires a long period of time. Also, limitations are imposed on the electrode materials that can be used in a system of applying the electrode material before baking, because the baking temperature must be set to a temperature equal to or greater than either the boiling point of stainless steel (SUS) or nickel (Ni), or the temperature that accompanies oxidizing deterioration. Therefore, sometimes the electrode cannot be formed by plating or another such simple method, which restricts the process.
Also, the hydrothermal synthesis method disclosed in Japanese Patent Application Publication No. 8-336967 is impractical because the base that can be used is mostly limited to titanium, and therefore there is no freedom in choosing the base material, and also because the film adheres slowly.